The work proposed concerns two major areas of study: I. Analysis of the relationship between long range cis transcriptional regulatory effects and synapsis-dependent trans regulatory effects in Drosophila: Our analysis to date suggests that these two classes of effects result from the properties of the same regulatory elements - enhancers or enhancer-like elements. If this relationship proves to be general, it represents a fundamentally new insight into the intractable problems of how enhancers work and what transvection effects are. Lines of experimentation include (a) identifying cases of activation of heterologous promotors by the presumptive enhancer at the white locus of Drosophila under conditions that allow convenient test for a corresponding synapsis dependent trans effect and (b) defining the portions of a promoter whose expression apparently represses (in cis and in synapsed trans) white expression when the two are juxtaposed in the w-DZL allele. II. Analysis of supressor-of-white-apricot and suppressor-of-white-spotted, two genes that apparently code for diffusable, trans-acting transcription factors: These genes represesnt two of the best opportunities in metazoan biology to study trans-acting transcription factors. Both of these genes are amenable to sophisticated genetic manipulation and we have cloned and partially analyzed the transcription units at both loci. The su(w-sp) gene behaves as if it codes for a repressor of white transcription and lines of experimentation include characterization of the tissue- and subcellular localization of the protein product of this locus with the objective of defining its role in regulating white transcription. The su(w-a) gene appears to activate its own transcription and lines of experimentation include definitive tests of this hypothesis and analysis of the cis-acting elements at su(w-a) responsive to the presumptive positive autoregulatory signal.